Systems and methods for bleeder control related to lighting emitting diodes

ABSTRACT

System and method for controlling one or more light emitting diodes. For example, the system includes a bleeder configured to receive a rectified voltage generated by a rectifying bridge, and a dimmer detector configured to receive an input voltage generated by a voltage divider, determine whether or not the rectified voltage is associated with a TRIAC dimmer, and output a control signal to the bleeder. The voltage divider is configured to receive the rectified voltage, and the input voltage indicates a magnitude of the rectified voltage.

1. CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No.201710828263.5, filed Sep. 14, 2017, incorporated by reference hereinfor all purposes.

2. BACKGROUND OF THE INVENTION

Certain embodiments of the present invention are directed to circuits.More particularly, some embodiments of the invention provide systems andmethods for bleeder control. Merely by way of example, some embodimentsof the invention have been applied to light emitting diodes (LEDs). Butit would be recognized that the invention has a much broader range ofapplicability.

With development in the light-emitting diode (LED) lighting market, manyLED manufacturers have placed LED lighting products at an importantposition in market development. LED lighting products often need dimmertechnology to provide consumers with a unique visual experience. SinceTriode for Alternating Current (TRIAC) dimmers have been widely used inconventional lighting systems such as incandescent lighting systems, theTRIAC dimmers are also increasingly being used in LED lighting systems.

Conventionally, the TRIAC dimmers usually are designed primarily forincandescent lights with pure resistive loads and low luminousefficiency. Such characteristics of incandescent lights often help tomeet the requirements of TRIAC dimmers in holding currents. Therefore,the TRIAC dimmers usually are suitable for light dimming when used withincandescent lights.

However, when the TRIAC dimmers are used with more efficient LEDs, it isoften difficult to meet the requirements of TRIAC dimmers in holdingcurrents due to the reduced input power needed to achieve equivalentillumination to that of incandescent lights. Therefore, conventional LEDlighting systems often utilize bleeder units to provide compensation inorder to satisfy the requirements of TRIAC dimmers in holding currents.

FIG. 1 is an exemplary circuit diagram showing a conventional LEDlighting system using a TRIAC dimmer. As shown in FIG. 1, the maincontrol unit of the LED lighting system 100 includes a constant current(CC) unit U1 and a bleeder unit U2. The constant current unit U1controls constant current output of the LED lighting system 100. Thebleeder unit U2 provides a bleeder current of a certain magnitude tomaintain the TRIAC dimmer's normal operation and to prevent the TRIACdimmer from malfunctioning due to insufficient current supply.

The operation process of the LED lighting system 100 as shown in FIG. 1is as follows: after the system 100 is powered on, an AC input voltage(e.g., VAC) is received by the TRIAC dimmer and rectified by a full-waverectifier BD1 to generate a rectified voltage (e.g., VIN); the constantcurrent unit U1 generates a constant current for the LED lighting system100, and the constant current flows through the LED into the constantcurrent unit U1; using the TRIAC dimmer, the rectified voltage (e.g.,VIN) received by the anode of the LED usually has a waveform of an ACsignal that has been clipped and rectified. As an example, when thewaveform of the AC signal is clipped by the TRIAC dimmer or when therectified voltage (e.g., VIN) is relatively small in magnitude within anAC cycle, the LED does not conduct current because of the insufficientvoltage and does not have a current that flows through, causing theTRIAC dimmer to malfunction. Therefore, the bleeder unit U2 often isneeded to generate a sufficient bleeder current in the LED lightingsystem 100 to maintain the TRIAC dimmer in normal operation.

From the perspective of system power, the input power of the LEDlighting system 100 includes mainly the LED power and the bleeder power:

P _(in) =P _(led) +P _(bleeder)  (Equation 1)

where P_(in) represents the input power of the system 100, P_(led)represents the power consumed by the LED, and P_(bleeder) represents thepower consumed by the bleeder unit U2.

Hence it is highly desirable to improve the techniques related to LEDlighting systems.

3. BRIEF SUMMARY OF THE INVENTION

Certain embodiments of the present invention are directed to circuits.More particularly, some embodiments of the invention provide systems andmethods for bleeder control. Merely by way of example, some embodimentsof the invention have been applied to light emitting diodes (LEDs). Butit would be recognized that the invention has a much broader range ofapplicability.

According to some embodiments, a system for controlling one or morelight emitting diodes includes a bleeder configured to receive arectified voltage generated by a rectifying bridge, and a dimmerdetector configured to receive an input voltage generated by a voltagedivider, determine whether or not the rectified voltage is associatedwith a TRIAC dimmer, and output a control signal to the bleeder. Thevoltage divider is configured to receive the rectified voltage, and theinput voltage indicates a magnitude of the rectified voltage. The dimmerdetector is further configured to determine that the rectified voltageis associated with a TRIAC dimmer if a first time duration for therectified voltage to increase from a first voltage to a second voltageis smaller than a first predetermined duration or a second time durationfor the rectified voltage to decrease from the second voltage to thefirst voltage is smaller than a second predetermined duration. Thedimmer detector is further configured to: generate the control signal toturn on the bleeder if the rectified voltage is determined to beassociated with a TRIAC dimmer so that the bleeder generates a firstcurrent, the first current being larger than zero in magnitude; andgenerate the control signal to turn off the bleeder if the rectifiedvoltage is determined not to be associated with any TRIAC dimmer so thatthe bleeder does not generate the first current.

According to certain embodiments, a method for controlling one or morelight emitting diodes includes receiving an input voltage. The inputvoltage indicates a magnitude of a rectified voltage generated by arectifying bridge. Additionally, the method includes determining whetheror not the rectified voltage is associated with a TRIAC dimmer, andoutputting a control signal to a bleeder. The determining whether or notthe rectified voltage is associated with a TRIAC dimmer includes:determining that the rectified voltage is associated with a TRIAC dimmerif a first time duration for the rectified voltage to increase from afirst voltage to a second voltage is smaller than a first predeterminedduration or a second time duration for the rectified voltage to decreasefrom the second voltage to the first voltage is smaller than a secondpredetermined duration. The outputting a control signal to a bleederincludes: generating the control signal to turn on the bleeder if therectified voltage is determined to be associated with a TRIAC dimmer sothat the bleeder generates a first current, the first current beinglarger than zero in magnitude; and generating the control signal to turnoff the bleeder if the rectified voltage is determined not to beassociated with any TRIAC dimmer so that the bleeder does not generatethe first current.

According to some embodiments, a system for controlling one or morelight emitting diodes includes a bleeder configured to receive arectified voltage generated by a rectifying bridge, and a dimmerdetector configured to receive an input voltage generated by a voltagedivider, determine whether or not the rectified voltage is associatedwith a TRIAC dimmer, and output a control signal to the bleeder. Thevoltage divider is configured to receive a first voltage received by therectifying bridge, and the input voltage indicates a magnitude of thefirst voltage. The dimmer detector is further configured to determinethat the rectified voltage is associated with a TRIAC dimmer if a firsttime duration for an absolute value of the first voltage to increasefrom a first voltage to a second voltage is smaller than a firstpredetermined duration or a second time duration for the absolute valueof the first voltage to decrease from the second voltage to the firstvoltage is smaller than a second predetermined duration. The dimmerdetector is further configured to generate the control signal to turn onthe bleeder if the rectified voltage is determined to be associated witha TRIAC dimmer so that the bleeder generates a first current, the firstcurrent being larger than zero in magnitude, and generate the controlsignal to turn off the bleeder if the rectified voltage is determinednot to be associated with any TRIAC dimmer so that the bleeder does notgenerate the first current.

According to certain embodiments, a method for controlling one or morelight emitting diodes includes receiving an input voltage. The inputvoltage indicates a magnitude of a first voltage received by arectifying bridge, and the rectifying bridge is configured to generate arectified voltage. Additionally, the method includes determining whetheror not the rectified voltage is associated with a TRIAC dimmer, andoutputting a control signal to a bleeder. The determining whether or notthe rectified voltage is associated with a TRIAC dimmer includes:determining that the rectified voltage is associated with a TRIAC dimmerif a first time duration for an absolute value of the first voltage toincrease from a first voltage to a second voltage is smaller than afirst predetermined duration or a second time duration for the absolutevalue of the first voltage to decrease from the second voltage to thefirst voltage is smaller than a second predetermined duration. Theoutputting a control signal to a bleeder includes: generating thecontrol signal to turn on the bleeder if the rectified voltage isdetermined to be associated with a TRIAC dimmer so that the bleedergenerates a first current, the first current being larger than zero inmagnitude; and generating the control signal to turn off the bleeder ifthe rectified voltage is determined not to be associated with any TRIACdimmer so that the bleeder does not generate the first current.

4. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary circuit diagram showing a conventional LEDlighting system using a TRIAC dimmer.

FIG. 2 is a simplified circuit diagram showing an LED lighting systemaccording to some embodiments of the present invention.

FIG. 3 shows simplified timing diagrams if no TRIAC dimmer is includedin the LED lighting system as shown in FIG. 2 according to certainembodiments of the present invention.

FIG. 4 is a simplified diagram showing a method for determining whetheror not a TRIAC dimmer is included in the LED lighting system as shown inFIG. 2 according to some embodiments of the present invention.

FIG. 5 is a simplified circuit diagram showing an LED lighting systemaccording to certain embodiments of the present invention.

Depending upon embodiment, one or more benefits may be achieved. Thesebenefits and various additional objects, features and advantages of thepresent invention can be fully appreciated with reference to thedetailed description and accompanying drawings that follow.

5. DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the present invention are directed to circuits.More particularly, some embodiments of the invention provide systems andmethods for bleeder control. Merely by way of example, some embodimentsof the invention have been applied to light emitting diodes (LEDs). Butit would be recognized that the invention has a much broader range ofapplicability.

For example, an LED lighting system needs to operate efficiently with orwithout a TRIAC dimmer. As an example, without a TRIAC dimmer, there isno need to generate a bleeder current for maintaining the normaloperation of the TRIAC dimmer, so the bleeder current generated by ableeder unit wastes system power and lowers the system efficiency.

According to certain embodiments, an LED lighting system for use with aTRIAC dimmer is provided. In some examples, an LED lighting system isconfigured to determine whether the LED lighting system includes a TRIACdimmer based on a change in the rectified voltage that is detected whenthe lighting system is powered-on. In certain examples, the LED lightingsystem enables (e.g., turns on) and disables (e.g., turns off) thebleeder unit in response to whether or not a TRIAC dimmer is included(e.g., connected) in the LED lighting system. For example, if a dimmerdetection unit determines that the LED lighting system includes a TRIACdimmer, the system enables (e.g., turns on) the bleeder unit. As anexample, if the dimmer detection unit determines that the LED lightingsystem does not include any TRIAC dimmer, the system disables (e.g.,turns off) the bleeder unit. In some examples, the system adaptivelyeliminates the waste of system power that is caused by the bleeder unitwhen the LED lighting system does not include any TRIAC dimmer, therebyimproving the system efficiency.

FIG. 2 is a simplified circuit diagram showing an LED lighting systemaccording to some embodiments of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown in FIG. 2, thecontroller of the LED lighting system 200 includes a constant currentunit 210 (e.g., a constant current unit U1), a bleeder unit 220 (e.g., ableeder unit U2), and a dimmer detection unit 230 (e.g., a dimmerdetection unit U3). As an example, the system 200 includes a line (L)terminal and a neutral (N) terminal. For example, the constant currentunit 210 is configured to generate a constant current that flows throughthe LED into the constant current unit 210. Although the above has beenshown using a selected group of components for the LED lighting system,there can be many alternatives, modifications, and variations. Forexample, some of the components may be expanded and/or combined. Othercomponents may be inserted to those noted above. Depending upon theembodiment, the arrangement of components may be interchanged withothers replaced. Further details of these components are foundthroughout the present specification.

In one embodiment, the LED lighting system 200 includes a TRIAC dimmer290. For example, a full wave rectifying bridge 292 (e.g., a full waverectifying bridge BD1) is coupled to the TRIAC dimmer 290 through a fuse294, and an AC input voltage (e.g., VAC) is received by the TRIAC dimmer290 and is also rectified by the full wave rectifying bridge 292 togenerate a rectified voltage 201 (e.g., VIN). As an example, therectified voltage 201 does not fall below the ground voltage of the chip(e.g., zero volts).

In another embodiment, the LED lighting system 200 does not include theTRIAC dimmer 290. For example, the AC input voltage (e.g., VAC) isreceived by the full wave rectifying bridge 292 (e.g., the full waverectifying bridge BD1) through the fuse 294, and is also rectified bythe full wave rectifying bridge 292 to generate the rectified voltage201 (e.g., VIN). As an example, the rectified voltage 201 does not fallbelow the ground voltage of the chip (e.g., zero volts).

In some embodiments, if the LED lighting system 200 includes a TRIACdimmer (e.g., the TRIAC dimmer 290), the rectified voltage 201 isassociated with the TRIAC dimmer (e.g., the TRIAC dimmer 290). Forexample, the rectified voltage 201 has a waveform that is clipped by theTRIAC dimmer (e.g., the TRIAC dimmer 290). In certain embodiments, ifthe LED lighting system 200 does not include any TRIAC dimmer (e.g., theTRIAC dimmer 290), the rectified voltage 201 is not associated with anyTRIAC dimmer (e.g., the TRIAC dimmer 290). For example, the rectifiedvoltage 201 has a waveform that is not clipped by any TRIAC dimmer(e.g., the TRIAC dimmer 290).

According to some embodiments, the LED lighting system 200 includes aresistor 240 (e.g., the resistor R1) and a resistor 242 (e.g., theresistor R2). In some examples, the resistors 240 and 242 are parts of avoltage divider biased between the rectified voltage 201 (e.g., VIN) andthe ground voltage. For example, one terminal of the resistor 240 isbiased at the rectified voltage 201 (e.g., VIN), one terminal of theresistor 242 is biased at the ground voltage, and another terminal ofthe resistor 240 and another terminal of the resistor 242 are connectedto provide a voltage 244 (e.g., at a node VA). As an example, thevoltage 244 indicates the magnitude of the rectified voltage 201 (e.g.,VIN), and the voltage 244 is received by the dimmer detection unit 230(e.g., a dimmer detector). In certain examples, the dimmer detectionunit 230 (e.g., a dimmer detector) outputs a control signal 232 (e.g., ableed_off signal) to the bleeder unit 220 (e.g., a bleeder). Forexample, the control signal 232 (e.g., the bleed-off signal) is used toenable (e.g., turn on) or disable (e.g., turn off) the bleeder unit 220(e.g., a bleeder).

According to certain embodiments, the operation of the LED lightingsystem 200 as shown in FIG. 2 is as follows: after the system 200 ispowered on, the dimmer detection unit 230 (e.g., a dimmer detector)determines whether or not a TRIAC dimmer (e.g., the TRIAC dimmer 290) isincluded (e.g., connected) in the LED lighting system 200 in response toa change in the voltage 244 (e.g., at the node VA). For example, if thedimmer detection unit 230 determines that a TRIAC dimmer (e.g., theTRIAC dimmer 290) is included (e.g., connected) in the LED lightingsystem 200, the dimmer detection unit 230 enables (e.g., turns on) thebleeder unit 220 (e.g., a bleeder) to operate. As an example, if thedimmer detection unit 230 determines that no TRIAC dimmer (e.g., theTRIAC dimmer 290) is included (e.g., connected) in the LED lightingsystem 200, the dimmer detection unit 230 disables (e.g., turns off) thebleeder unit 220 (e.g., a bleeder).

In some embodiments, if the LED lighting system 200 includes a TRIACdimmer (e.g., the TRIAC dimmer 290), even if the TRIAC dimmer (e.g., theTRIAC dimmer 290) is set to its maximum dimming angle that correspondsto the strongest luminance for LED, the rectified voltage 201 (e.g.,VIN) is still clipped by the TRIAC dimmer (e.g., the TRIAC dimmer 290),causing a sudden change in the rectified voltage 201 (e.g., VIN) withineach half cycle of the AC input voltage (e.g., VAC). For example, if theLED lighting system 200 includes a leading-edge TRIAC dimmer (e.g., theTRIAC dimmer 290 being a leading-edge dimmer), the rectified voltage 201(e.g., VIN) increases within a short time duration within a half cycleof the AC input voltage (e.g., VAC). In another example, if the LEDlighting system 200 includes a trailing-edge TRIAC dimmer (e.g., theTRIAC dimmer 290 being a trailing-edge dimmer), the rectified voltage201 (e.g., VIN) decreases within a short time duration within a halfcycle of the AC input voltage (e.g., VAC). In certain embodiments, amethod for controlling the LED lighting system 200 is provided as shownin FIG. 4 as an example.

As discussed above and further emphasized here, FIG. 2 is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. For example, the LED lighting system 200 isconfigured to provide power to one or more LEDs. As an example, multipleLEDs are connected in series and configured to receive the rectifiedvoltage 201 (e.g., VIN) as shown in FIG. 2.

FIG. 3 and FIG. 4 are simplified diagrams showing a method forcontrolling the LED lighting system 200 according to some embodiments ofthe present invention. These diagrams are merely examples, which shouldnot unduly limit the scope of the claims. One of ordinary skill in theart would recognize many variations, alternatives, and modifications.

In certain embodiments, FIG. 4 is a simplified diagram showing a methodfor determining whether or not a TRIAC dimmer (e.g., the TRIAC dimmer290) is included (e.g., connected) in the LED lighting system 200. Forexample, as shown in FIG. 4, the method 400 includes processes S402,S404, S406, S408 and S410. As an example, the change in the rectifiedvoltage 201 (e.g., VIN) at the node VA is monitored and/or used to helpdetermine whether a TRIAC dimmer (e.g., the TRIAC dimmer 290) isincluded (e.g., connected) in the LED lighting system 200.

At the process S402, the dimmer detection unit 230 (e.g., the dimmerdetection unit U3) determines whether or not the time duration duringwhich the rectified voltage 201 (e.g., VIN) rises from a firstpredetermined voltage V₁ to a second predetermined voltage V₂ is smallerthan a first predetermined time duration T₀₁ according to oneembodiment. In some examples, the rectified voltage 201 becomes largerthan the first predetermined voltage V₁ at time t₁ and becomes largerthan the second predetermined voltage V₂ at time t₂, where the secondpredetermined voltage V₂ is larger than the first predetermined voltageV₁. For example, the dimmer detection unit 230 determines the time t₁when the voltage 244 becomes larger than a first predeterminedthreshold, where a ratio of the first predetermined threshold to thefirst predetermined voltage V₁ is equal to a ratio of the voltage 244 tothe rectified voltage 201. As an example, the dimmer detection unit 230determines the time t₂ when the voltage 244 becomes larger than a secondpredetermined threshold, where a ratio of the second predeterminedthreshold to the second predetermined voltage V₂ is equal to a ratio ofthe voltage 244 to the rectified voltage 201. In certain examples, thedimmer detection unit 230 determines whether or not the time durationfrom time t₁ to time t₂ is smaller than the first predetermined timeduration T₀₁, where the time duration from time t₁ to time t₂ is, forexample, the time duration during which the rectified voltage 201 (e.g.,VIN) rises from the first predetermined voltage V₁ to the secondpredetermined voltage V₂.

In one example, if the time duration during which the rectified voltage201 (e.g., VIN) rises from the first predetermined voltage V₁ to thesecond predetermined voltage V₂ is determined to be smaller than thefirst predetermined time duration T₀₁, the process S404 is performed. Inanother example, if the time duration during which the rectified voltage201 (e.g., VIN) rises from the first predetermined voltage V₁ to thesecond predetermined voltage V₂ is determined not to be smaller than thefirst predetermined time duration T₀₁, the process S408 is performed.

At the process S406, the dimmer detection unit 230 (e.g., the dimmerdetection unit U3) determines whether or not the time duration duringwhich the rectified voltage 201 (e.g., VIN) drops from the secondpredetermined voltage V₂ to the first predetermined voltage V₁ issmaller than a second predetermined time duration T₀₂ according to oneembodiment. In some examples, the rectified voltage 201 becomes smallerthan the second predetermined voltage V₂ at time t₃ and becomes smallerthan the first predetermined voltage V₁ at time t₄, where the secondpredetermined voltage V₂ is larger than the first predetermined voltageV₁. For example, the dimmer detection unit 230 determines the time t₃when the voltage 244 becomes smaller than the second predeterminedthreshold, where a ratio of the second predetermined threshold to thesecond predetermined voltage V₂ is equal to a ratio of the voltage 244to the rectified voltage 201. As an example, the dimmer detection unit230 determines the time t₄ when the voltage 244 becomes smaller than thefirst predetermined threshold, where a ratio of the first predeterminedthreshold to the first predetermined voltage V₁ is equal to a ratio ofthe voltage 244 to the rectified voltage 201. In certain examples, thedimmer detection unit 230 determines whether or not the time durationfrom time t₃ to time t₄ is smaller than the second predetermined timeduration T₀₂, where the time duration from time t₃ to time t₄ is, forexample, the time duration during which the rectified voltage 201 (e.g.,VIN) drops from the second predetermined voltage V₂ to the firstpredetermined voltage V₁. As an example, the first predetermined timeduration T₀₁ is equal to the second predetermined time duration T₀₂. Forexample, the first predetermined time duration T₀₁ is not equal to thesecond predetermined time duration T₀₂.

In one example, if the time duration during which the rectified voltage201 (e.g., VIN) drops from the second predetermined voltage V₂ to thefirst predetermined voltage V₁ is determined to be smaller than thesecond predetermined time duration T₀₂, the process S404 is performed.In another example, if the time duration during which the rectifiedvoltage 201 (e.g., VIN) drops from the second predetermined voltage V₂to the first predetermined voltage V₁ is determined not to be smallerthan the second predetermined time duration T₀₂, the process S408 isperformed.

At the process S404, the dimmer detection unit 230 generates the controlsignal 232 (e.g., the bleed_off signal) at a first logic level (e.g., alogic low level) and outputs the control signal 232 to enable (e.g.,turn on) the bleeder unit 220 according to one embodiment. For example,the control signal 232 at the first logic level indicates that a TRIACdimmer (e.g., the TRIAC dimmer 290) is included (e.g., connected) in theLED lighting system 200. In some examples, the bleeder unit 220 isturned on so that a bleeder current 222 is generated (e.g., the bleedercurrent 222 being larger than zero in magnitude). For example, when theLED lighting system 200 includes a TRIAC dimmer (e.g., the TRIAC dimmer290), the bleeder unit 220 generates the bleeder current 222 so that acurrent that flows through the TRIAC dimmer 290 does not fall below aholding current of the TRIAC dimmer 290.

At the process S408, the dimmer detection unit 230 generates the controlsignal 232 (e.g., the bleed_off signal) at a second logic level (e.g., alogic high level) and outputs the control signal 232 to disable (e.g.,turn off) the bleeder unit 220 according to one embodiment. For example,the control signal 232 at the second logic level indicates that no TRIACdimmer is included (e.g., connected) in the LED lighting system 200. Insome examples, the bleeder unit 220 is turned off so that the bleedercurrent 222 is not generated (e.g., the bleeder current 222 being equalto zero in magnitude). As an example, when the LED lighting system 200does not include any TRIAC dimmer, the bleeder unit 220 does not providethe bleeder current 222 (e.g., the bleeder current 222 being equal tozero in magnitude).

At the process S410, the LED lighting system 200 operates normally. Forexample, if the LED lighting system 200 includes a TRIAC dimmer (e.g.,the TRIAC dimmer 290), the bleeder unit 220 generates the bleedercurrent 222 that is sufficient for the TRIAC dimmer 290 to worknormally. In another example, if the LED lighting system 200 does notinclude any TRIAC dimmer (e.g., the TRIAC dimmer 290), the bleeder unit220 does not need to provide the bleeder current 222 in order for theLED lighting system 200 to operate normally.

As discussed above and further emphasized here, FIG. 4 is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. According to some embodiments, for the same halfcycle of the AC input voltage (e.g., VAC), the process S406 is startedbefore the process S402 is completed. For example, within one half cycleof the AC input voltage (e.g., VAC), the dimmer detection unit 230,determines the time t₃, at which the rectified voltage 201 becomessmaller than the second predetermined voltage V₂, and also determinesthe time t₄, at which the rectified voltage 201 becomes smaller than thefirst predetermined voltage V₁, when the dimmer detection unit 230compares the time duration during which the rectified voltage 201 (e.g.,VIN) rises from the first predetermined voltage V₁ to the secondpredetermined voltage V₂ with the first predetermined time duration T₀₁.

According to certain embodiments, the process S402 is started for onehalf cycle of the AC input voltage (e.g., VAC) before the process S406is completed for the previous half cycle of the AC input voltage (e.g.,VAC). For example, the dimmer detection unit 230, for one half cycle ofthe AC input voltage (e.g., VAC), determines the time t₁, at which therectified voltage 201 becomes larger than the first predeterminedvoltage V₁, and also determines the time t₂, at which the rectifiedvoltage 201 becomes larger than the second predetermined voltage V₂,when the dimmer detection unit 230, for the previous half cycle of theAC input voltage (e.g., VAC), compares the time duration during whichthe rectified voltage 201 (e.g., VIN) drops from the secondpredetermined voltage V₂ to the first predetermined voltage V₁ with thesecond predetermined time duration T₀₂.

According to some embodiments, if the dimmer detection unit 230 (e.g.,the dimmer detection unit U3) determines that the time duration duringwhich the rectified voltage 201 (e.g., VIN) rises from the firstpredetermined voltage V₁ to the second predetermined voltage V₂ issmaller than the first predetermined time duration T₀₁ at the processS402, and the dimmer detection unit 230 (e.g., the dimmer detection unitU3) also determines that the time duration during which the rectifiedvoltage 201 (e.g., VIN) drops from the second predetermined voltage V₂to the first predetermined voltage V₁ is smaller than the secondpredetermined time duration T₀₂ at the process S406, the dimmerdetection unit 230 generates the control signal 232 (e.g., the bleed_offsignal) at the first logic level (e.g., a logic low level) and outputsthe control signal 232 to enable (e.g., turn on) the bleeder unit 220 atthe process S404.

According to certain embodiments, FIG. 3 shows simplified timingdiagrams if no TRIAC dimmer is included (e.g., connected) in the LEDlighting system 200. In some examples, the waveform 310 represents therectified voltage 201 (e.g., VIN) as a function of time, and thewaveform 320 represents the control signal 232 (e.g., the bleed_offsignal) as a function of time.

In some examples, as shown by the waveform 320, for the previous halfcycle of the AC input voltage (e.g., VAC), the control signal 232 (e.g.,the bleed_off signal) has been determined to be at a first logic level(e.g., a logic low level) in order to enable (e.g., turn on) the bleederunit 220. As an example, as shown by the waveform 320, at the beginningof a half cycle after the previous half cycle of the AC input voltage(e.g., VAC), the control signal 232 (e.g., the bleed_off signal) remainsat the first logic level (e.g., the logic low level) and the bleederunit 220 remains enabled (e.g., turned-on).

In certain examples, as shown by the waveform 310, the rectified voltage201 (e.g., VIN) becomes larger than a first predetermined voltage V₁ attime t₁, and becomes larger than a second predetermined voltage V₂ attime t₂. As an example, as shown by the waveform 310, the rectifiedvoltage 201 (e.g., VIN) becomes smaller than the second predeterminedvoltage V₂ at time t₃, and becomes smaller than the first predeterminedvoltage V₁ at time t₄.

In some embodiments, at the process S402, the dimmer detection unit 230determines that the time duration from time t₁ to time t₂ is not smallerthan the first predetermined time duration T₀₁, where the time durationfrom time t₁ to time t₂ is, for example, the time duration during whichthe rectified voltage 201 (e.g., VIN) rises from the first predeterminedvoltage V₁ to the second predetermined voltage V₂. As an example, inresponse to this comparison result, the process S406 is then performed.For example, before the process S406 is completed, the control signal232 (e.g., the bleed_off-off signal) remains at the first logic level(e.g., the logic low level) and the bleeder unit 220 remains enabled(e.g., turned-on), as shown by the waveform 320.

In certain embodiments, at the process S406, the dimmer detection unit230 determines that the time duration from time t₃ to time t₄ is notsmaller than the second predetermined time duration T₀₂, where the timeduration from time t₃ to time t₄ is, for example, the time durationduring which the rectified voltage 201 (e.g., VIN) drops from the secondpredetermined voltage V₂ to the first predetermined voltage V₁. As anexample, in response to this comparison result, the process S408 is thenperformed. In some embodiments, at the process S408, the dimmerdetection unit 230 changes the control signal 232 (e.g., the bleed_offsignal) from the first logic level (e.g., the logic low level) to asecond logic level (e.g., a logic high level) to disable (e.g., turnoff) the bleeder unit 220, as shown by the waveform 320.

According to certain embodiments, the LED lighting system 200 and themethod 400 for determining whether or not a TRIAC dimmer (e.g., theTRIAC dimmer 290) is included (e.g., connected) in the LED lightingsystem 200 are compatible regardless of whether the LED lighting system200 includes any TRIAC dimmer. For example, the system LED lightingsystem 200 adaptively eliminates the waste of system power that may becaused by the bleeder unit 220 if the bleeder current 222 were generatedwhen the LED lighting system 200 does not include any TRIAC dimmer,thereby improving the system efficiency.

FIG. 5 is a simplified circuit diagram showing an LED lighting systemaccording to certain embodiments of the present invention. This diagramis merely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown in FIG. 5, thecontroller of the LED lighting system 500 includes a constant currentunit 510 (e.g., a constant current unit U1), a bleeder unit 520 (e.g., ableeder unit U2), and a dimmer detection unit 530 (e.g., a dimmerdetection unit U3). As an example, the system 500 includes a line (L)terminal and a neutral (N) terminal. For example, the constant currentunit 510 is configured to generate a constant current that flows throughthe LED into the constant current unit 510. Although the above has beenshown using a selected group of components for the LED lighting system,there can be many alternatives, modifications, and variations. Forexample, some of the components may be expanded and/or combined. Othercomponents may be inserted to those noted above. Depending upon theembodiment, the arrangement of components may be interchanged withothers replaced. Further details of these components are foundthroughout the present specification.

In one embodiment, the LED lighting system 500 includes a TRIAC dimmer590. For example, a full wave rectifying bridge 592 (e.g., a full waverectifying bridge BD1) is coupled to the TRIAC dimmer 590 through a fuse594. As an example, an AC input voltage (e.g., VAC) is received by theTRIAC dimmer 590, which generates a voltage 596 (e.g., the TRIAC dimmer590 generating the voltage 596 through the fuse 594). As an example, thevoltage 596 is rectified by the full wave rectifying bridge 592 togenerate a rectified voltage 501 (e.g., VIN). For example, the rectifiedvoltage 501 does not fall below the ground voltage of the chip (e.g.,zero volts). In another embodiment, the LED lighting system 500 does notinclude the TRIAC dimmer 590. For example, the AC input voltage (e.g.,VAC) is received by the full wave rectifying bridge 592 (e.g., the fullwave rectifying bridge BD1) through the fuse 594 as the voltage 596. Asan example, the voltage 596 is rectified by the full wave rectifyingbridge 592 to generate the rectified voltage 501 (e.g., VIN). Forexample, the rectified voltage 501 does not fall below the groundvoltage of the chip (e.g., zero volts).

According to some embodiments, if the LED lighting system 500 includes aTRIAC dimmer (e.g., the TRIAC dimmer 590), the rectified voltage 501 isassociated with the TRIAC dimmer (e.g., the TRIAC dimmer 590). Forexample, the rectified voltage 501 has a waveform that is clipped by theTRIAC dimmer (e.g., the TRIAC dimmer 590). According to certainembodiments, if the LED lighting system 500 does not include any TRIACdimmer (e.g., the TRIAC dimmer 590), the rectified voltage 501 is notassociated with any TRIAC dimmer (e.g., the TRIAC dimmer 590). Forexample, the rectified voltage 501 has a waveform that is not clipped byany TRIAC dimmer (e.g., the TRIAC dimmer 590).

In some embodiments, if the LED lighting system 500 includes a TRIACdimmer (e.g., the TRIAC dimmer 590), the voltage 596 is associated withthe TRIAC dimmer (e.g., the TRIAC dimmer 590). For example, the voltage596 has a waveform that is clipped by the TRIAC dimmer (e.g., the TRIACdimmer 590). In certain embodiments, if the LED lighting system 500 doesnot include any TRIAC dimmer (e.g., the TRIAC dimmer 590), the voltage596 is not associated with any TRIAC dimmer (e.g., the TRIAC dimmer590). For example, the voltage 596 has a waveform that is not clipped byany TRIAC dimmer (e.g., the TRIAC dimmer 590).

According to some embodiments, the LED lighting system 500 includes acombination of a resistor 540 (e.g., a resistor R1), a resistor 542(e.g., a resistor R2), and a resistor 546 (e.g., a resistor R3). Forexample, the resistors 540, 542 and 546 are parts of a voltage divider.As an example, the resistor 540 is configured to receive the voltage596, and another terminal of the resistor 540 is connected to oneterminal of the resistor 542 and one terminal of the resistor 546. Forexample, the one terminal of the resistor 546 is configured to provide avoltage 544 (e.g., at a node VA). As an example, another terminal of theresistor 546 is biased to the ground voltage, and another terminal ofthe resistor 542 is connected to the N terminal of the system 500. Forexample, the voltage 544 indicates the magnitude of the voltage 596, andthe absolute value of the voltage 544 indicates the absolute value ofthe voltage 596. As an example, the voltage 544 is received by thedimmer detection unit 530 (e.g., a dimmer detector). In certainexamples, the dimmer detection unit 530 (e.g., a dimmer detector)outputs a control signal 532 (e.g., a bleed_off signal) to the bleederunit 520 (e.g., a bleeder). For example, the control signal 532 (e.g.,the bleed-off signal) is used to enable (e.g., turn on) or disable(e.g., turn off) the bleeder unit 520 (e.g., a bleeder).

According to certain embodiments, the operation of the LED lightingsystem 500 as shown in FIG. 5 is as follows: after the system 500 ispowered on, the dimmer detection unit 530 (e.g., a dimmer detector)determines whether or not a TRIAC dimmer (e.g., the TRIAC dimmer 590) isincluded (e.g., connected) in the LED lighting system 500 in response toa change in the voltage 544 (e.g., at the node VA). For example, if thedimmer detection unit 530 determines that a TRIAC dimmer (e.g., theTRIAC dimmer 590) is included (e.g., connected) in the LED lightingsystem 500, the dimmer detection unit 530 enables (e.g., turns on) thebleeder unit 520 (e.g., a bleeder) to operate. As an example, if thedimmer detection unit 530 determines that no TRIAC dimmer (e.g., theTRIAC dimmer 590) is included (e.g., connected) in the LED lightingsystem 500, the dimmer detection unit 530 disables (e.g., turns off) thebleeder unit 520 (e.g., a bleeder).

In some embodiments, if the LED lighting system 500 includes a TRIACdimmer (e.g., the TRIAC dimmer 590), even if the TRIAC dimmer (e.g., theTRIAC dimmer 590) is set to its maximum dimming angle that correspondsto the strongest luminance for LED, the voltage 596 is still clipped bythe TRIAC dimmer (e.g., the TRIAC dimmer 590), causing a sudden changein the voltage 596 (e.g., VIN) within each half cycle of the AC inputvoltage (e.g., VAC). For example, if the LED lighting system 500includes a leading-edge TRIAC dimmer (e.g., the TRIAC dimmer 590 being aleading-edge dimmer), the absolute value of the voltage 596 increaseswithin a short time duration within a half cycle of the AC input voltage(e.g., VAC). In another example, if the LED lighting system 500 includesa trailing-edge TRIAC dimmer (e.g., the TRIAC dimmer 590 being atrailing-edge dimmer), the absolute value of the voltage 596 decreaseswithin a short time duration within a half cycle of the AC input voltage(e.g., VAC).

In some embodiments, FIG. 3 shows simplified timing diagrams if no TRIACdimmer is included (e.g., connected) in the LED lighting system 500, andif the waveform 310 represents the absolute value of the voltage 596 asa function of time and the waveform 320 represents the control signal532 (e.g., the bleed_off signal) as a function of time. In certainembodiments, FIG. 4 shows a simplified diagram for a method ofdetermining whether or not a TRIAC dimmer (e.g., the TRIAC dimmer 590)is included (e.g., connected) in the LED lighting system 500, if, forexample, the change in the absolute value of the voltage 596 at the nodeVA is monitored and/or used to help determine whether a TRIAC dimmer(e.g., the TRIAC dimmer 590) is included (e.g., connected) in the LEDlighting system 500.

As discussed above and further emphasized here, FIG. 5 is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. For example, the LED lighting system 500 isconfigured to provide power to one or more LEDs. As an example, multipleLEDs are connected in series and configured to receive the rectifiedvoltage 501 (e.g., VIN) as shown in FIG. 5.

According to some embodiments, a system for controlling one or morelight emitting diodes includes a bleeder configured to receive arectified voltage generated by a rectifying bridge, and a dimmerdetector configured to receive an input voltage generated by a voltagedivider, determine whether or not the rectified voltage is associatedwith a TRIAC dimmer, and output a control signal to the bleeder. Thevoltage divider is configured to receive the rectified voltage, and theinput voltage indicates a magnitude of the rectified voltage. The dimmerdetector is further configured to determine that the rectified voltageis associated with a TRIAC dimmer if a first time duration for therectified voltage to increase from a first voltage to a second voltageis smaller than a first predetermined duration or a second time durationfor the rectified voltage to decrease from the second voltage to thefirst voltage is smaller than a second predetermined duration. Thedimmer detector is further configured to: generate the control signal toturn on the bleeder if the rectified voltage is determined to beassociated with a TRIAC dimmer so that the bleeder generates a firstcurrent, the first current being larger than zero in magnitude; andgenerate the control signal to turn off the bleeder if the rectifiedvoltage is determined not to be associated with any TRIAC dimmer so thatthe bleeder does not generate the first current. For example, the systemis implemented according to at least FIG. 2 and/or FIG. 4.

As an example, the dimmer detector is further configured to determinethat the rectified voltage is associated with a TRIAC dimmer, the firsttime duration is larger than the first predetermined duration, and thesecond time duration is smaller than the second predetermined duration.For example, the dimmer detector is further configured to determine thatthe rectified voltage is not associated with any TRIAC dimmer if thefirst time duration is not smaller than the first predetermined durationand the second time duration is not smaller than the secondpredetermined duration. As an example, the dimmer detector is furtherconfigured to determine that the rectified voltage is not associatedwith any TRIAC dimmer, the first time duration is larger than the firstpredetermined duration, and the second time duration is larger than thesecond predetermined duration.

For example, the dimmer detector is further configured to determine thatthe rectified voltage is associated with a TRIAC dimmer, the first timeduration is smaller than the first predetermined duration, and thesecond time duration is smaller than the second predetermined duration.As an example, the voltage divider includes multiple resistors connectedin series and biased between the rectified voltage and a ground voltage.

For example, the dimmer detector is further configured to determinewhether or not the first time duration for the rectified voltage toincrease from the first voltage to the second voltage is smaller thanthe first predetermined duration based at least in part on a firstchange of the input voltage. As an example, the dimmer detector isfurther configured to determine whether or not the second time durationfor the rectified voltage to decrease from the second voltage to thefirst voltage is smaller than the second predetermined duration based atleast in part on a second change of the input voltage.

For example, the system further includes a current generator configuredto generate a second current flowing through one or more light emittingdiodes, the one or more light emitting diodes being configured toreceive the rectified voltage. As an example, the dimmer detector isfurther configured to generate the control signal to turn on the bleederif the rectified voltage is determined to be associated with a TRIACdimmer so that the bleeder generates the first current to keep a thirdcurrent flowing though the TRIAC dimmer from becoming smaller than aholding current of the TRIAC dimmer.

According to certain embodiments, a method for controlling one or morelight emitting diodes includes receiving an input voltage. The inputvoltage indicates a magnitude of a rectified voltage generated by arectifying bridge. Additionally, the method includes determining whetheror not the rectified voltage is associated with a TRIAC dimmer, andoutputting a control signal to a bleeder. The determining whether or notthe rectified voltage is associated with a TRIAC dimmer includes:determining that the rectified voltage is associated with a TRIAC dimmerif a first time duration for the rectified voltage to increase from afirst voltage to a second voltage is smaller than a first predeterminedduration or a second time duration for the rectified voltage to decreasefrom the second voltage to the first voltage is smaller than a secondpredetermined duration. The outputting a control signal to a bleederincludes: generating the control signal to turn on the bleeder if therectified voltage is determined to be associated with a TRIAC dimmer sothat the bleeder generates a first current, the first current beinglarger than zero in magnitude; and generating the control signal to turnoff the bleeder if the rectified voltage is determined not to beassociated with any TRIAC dimmer so that the bleeder does not generatethe first current. For example, the method is implemented according toat least FIG. 2 and/or FIG. 4.

As an example, the determining whether or not the rectified voltage isassociated with a TRIAC dimmer includes: determining that the rectifiedvoltage is associated with a TRIAC dimmer; wherein: the first timeduration is larger than the first predetermined duration; and the secondtime duration is smaller than the second predetermined duration. Forexample, the determining whether or not the rectified voltage isassociated with a TRIAC dimmer includes: determining that the rectifiedvoltage is not associated with any TRIAC dimmer if the first timeduration is not smaller than the first predetermined duration and thesecond time duration is not smaller than the second predeterminedduration. As an example, the determining whether or not the rectifiedvoltage is associated with a TRIAC dimmer includes: determining that therectified voltage is not associated with any TRIAC dimmer; wherein: thefirst time duration is larger than the first predetermined duration; andthe second time duration is larger than the second predeterminedduration.

For example, the determining whether or not the rectified voltage isassociated with a TRIAC dimmer includes: determining that the rectifiedvoltage is associated with a TRIAC dimmer; wherein: the first timeduration is smaller than the first predetermined duration; and thesecond time duration is smaller than the second predetermined duration.As an example, the determining that the rectified voltage is associatedwith a TRIAC dimmer if a first time duration for the rectified voltageto increase from a first voltage to a second voltage is smaller than afirst predetermined duration or a second time duration for the rectifiedvoltage to decrease from the second voltage to the first voltage issmaller than a second predetermined duration includes: determining thatthe first time duration for the rectified voltage to increase from thefirst voltage to the second voltage is smaller than the firstpredetermined duration based at least in part on a first change of theinput voltage.

For example, the determining that the rectified voltage is associatedwith a TRIAC dimmer if a first time duration for the rectified voltageto increase from a first voltage to a second voltage is smaller than afirst predetermined duration or a second time duration for the rectifiedvoltage to decrease from the second voltage to the first voltage issmaller than a second predetermined duration further includes:determining that the second time duration for the rectified voltage todecrease from the second voltage to the first voltage is smaller thanthe second predetermined duration based at least in part on a secondchange of the input voltage. As an example, the generating the controlsignal to turn on the bleeder if the rectified voltage is determined tobe associated with a TRIAC dimmer so that the bleeder generates a firstcurrent includes: generating the control signal to turn on the bleederif the rectified voltage is determined to be associated with the TRIACdimmer so that the bleeder generates the first current in order to keepa second current flowing though the TRIAC dimmer from becoming smallerthan a holding current of the TRIAC dimmer.

According to some embodiments, a system for controlling one or morelight emitting diodes includes a bleeder configured to receive arectified voltage generated by a rectifying bridge, and a dimmerdetector configured to receive an input voltage generated by a voltagedivider, determine whether or not the rectified voltage is associatedwith a TRIAC dimmer, and output a control signal to the bleeder. Thevoltage divider is configured to receive a first voltage received by therectifying bridge, and the input voltage indicates a magnitude of thefirst voltage. The dimmer detector is further configured to determinethat the rectified voltage is associated with a TRIAC dimmer if a firsttime duration for an absolute value of the first voltage to increasefrom a first voltage to a second voltage is smaller than a firstpredetermined duration or a second time duration for the absolute valueof the first voltage to decrease from the second voltage to the firstvoltage is smaller than a second predetermined duration. The dimmerdetector is further configured to generate the control signal to turn onthe bleeder if the rectified voltage is determined to be associated witha TRIAC dimmer so that the bleeder generates a first current, the firstcurrent being larger than zero in magnitude, and generate the controlsignal to turn off the bleeder if the rectified voltage is determinednot to be associated with any TRIAC dimmer so that the bleeder does notgenerate the first current. For example, the system is implementedaccording to at least FIG. 5.

As an example, the dimmer detector is further configured to determinethat the rectified voltage is associated with a TRIAC dimmer, the firsttime duration is larger than the first predetermined duration, and thesecond time duration is smaller than the second predetermined duration.For example, the dimmer detector is further configured to determine thatthe rectified voltage is not associated with any TRIAC dimmer if thefirst time duration is not smaller than the first predetermined durationand the second time duration is not smaller than the secondpredetermined duration. As an example, the dimmer detector is furtherconfigured to determine that the rectified voltage is not associatedwith any TRIM dimmer, the first time duration is larger than the firstpredetermined duration, and the second time duration is larger than thesecond predetermined duration.

For example, the dimmer detector is further configured to determine thatthe rectified voltage is associated with a TRIAC dimmer, the first timeduration is smaller than the first predetermined duration, and thesecond time duration is smaller than the second predetermined duration.As an example, the dimmer detector is further configured to determinewhether or not the first time duration for the absolute value of thefirst voltage to increase from the first voltage to the second voltageis smaller than the first predetermined duration based at least in parton a first change of the input voltage. For example, the dimmer detectoris further configured to determine whether or not the second timeduration for the absolute value of the first voltage to decrease fromthe second voltage to the first voltage is smaller than the secondpredetermined duration based at least in part on a second change of theinput voltage.

As an example, the system further includes a current generatorconfigured to generate a second current flowing through one or morelight emitting diodes, the one or more light emitting diodes beingconfigured to receive the rectified voltage. For example, the dimmerdetector is further configured to generate the control signal to turn onthe bleeder if the rectified voltage is determined to be associated witha TRIAC dimmer so that the bleeder generates the first current to keep athird current flowing though the TRIAC dimmer from becoming smaller thana holding current of the TRIAC dimmer.

According to certain embodiments, a method for controlling one or morelight emitting diodes includes receiving an input voltage. The inputvoltage indicates a magnitude of a first voltage received by arectifying bridge, and the rectifying bridge is configured to generate arectified voltage. Additionally, the method includes determining whetheror not the rectified voltage is associated with a TRIAC dimmer, andoutputting a control signal to a bleeder. The determining whether or notthe rectified voltage is associated with a TRIAC dimmer includes:determining that the rectified voltage is associated with a TRIAC dimmerif a first time duration for an absolute value of the first voltage toincrease from a first voltage to a second voltage is smaller than afirst predetermined duration or a second time duration for the absolutevalue of the first voltage to decrease from the second voltage to thefirst voltage is smaller than a second predetermined duration. Theoutputting a control signal to a bleeder includes: generating thecontrol signal to turn on the bleeder if the rectified voltage isdetermined to be associated with a TRIAC dimmer so that the bleedergenerates a first current, the first current being larger than zero inmagnitude; and generating the control signal to turn off the bleeder ifthe rectified voltage is determined not to be associated with any TRIACdimmer so that the bleeder does not generate the first current. Forexample, the method is implemented according to at least FIG. 5.

As an example, the determining whether or not the rectified voltage isassociated with a TRIAC dimmer includes: determining that the rectifiedvoltage is associated with a TRIAC dimmer; wherein: the first timeduration is larger than the first predetermined duration; and the secondtime duration is smaller than the second predetermined duration. Forexample, the determining whether or not the rectified voltage isassociated with a TRIAC dimmer includes: determining that the rectifiedvoltage is not associated with any TRIAC dimmer if the first timeduration is not smaller than the first predetermined duration and thesecond time duration is not smaller than the second predeterminedduration. As an example, the determining whether or not the rectifiedvoltage is associated with a TRIAC dimmer includes: determining that therectified voltage is not associated with any TRIAC dimmer; wherein: thefirst time duration is larger than the first predetermined duration; andthe second time duration is larger than the second predeterminedduration.

For example, the determining whether or not the rectified voltage isassociated with a TRIAC dimmer includes: determining that the rectifiedvoltage is associated with a TRIAC dimmer; wherein: the first timeduration is smaller than the first predetermined duration; and thesecond time duration is smaller than the second predetermined duration.As an example, the determining that the rectified voltage is associatedwith a TRIAC dimmer if a first time duration for the absolute value ofthe first voltage to increase from a first voltage to a second voltageis smaller than a first predetermined duration or a second time durationfor the absolute value of the first voltage to decrease from the secondvoltage to the first voltage is smaller than a second predeterminedduration includes: determining that the first time duration for theabsolute value of the first voltage to increase from the first voltageto the second voltage is smaller than the first predetermined durationbased at least in part on a first change of the input voltage.

For example, the determining that the rectified voltage is associatedwith a TRIM dimmer if a first time duration for the absolute value ofthe first voltage to increase from a first voltage to a second voltageis smaller than a first predetermined duration or a second time durationfor the absolute value of the first voltage to decrease from the secondvoltage to the first voltage is smaller than a second predeterminedduration further includes: determining that the second time duration forthe absolute value of the first voltage to decrease from the secondvoltage to the first voltage is smaller than the second predeterminedduration based at least in part on a second change of the input voltage.As an example, the generating the control signal to turn on the bleederif the rectified voltage is determined to be associated with a TRIACdimmer so that the bleeder generates a first current includes:generating the control signal to turn on the bleeder if the rectifiedvoltage is determined to be associated with the TRIAC dimmer so that thebleeder generates the first current in order to keep a second currentflowing though the TRIAC dimmer from becoming smaller than a holdingcurrent of the TRIAC dimmer.

In some embodiments, an LED lighting system includes a dimmer detectionunit and a bleeder unit. For example, the dimmer detection unitdetermines whether the LED lighting system is connected to a TRIACdimmer based on a change in an input voltage of the LED lighting system.As an example, the dimmer detection unit enables the bleeder unit whenthe determination result is positive and disables the bleeder controlunit when the determination result is negative. For example, the bleederunit provides a bleeder current sufficient for the TRIAC dimmer to worknormally when the LED lighting system is connected to the TRIAC dimmer.

In some examples, the dimmer detection unit determines that the LEDlighting system is connected to a TRIAC dimmer when the dimmer detectionunit detects a first time period smaller than a first predeterminedperiod, wherein the first time period is the time duration for the inputvoltage to rise from a first voltage to a second voltage.

In certain examples, the dimmer detection unit determines that the LEDlighting system is not connected to any TRIAC dimmer when the dimmerdetection unit detects a first time period greater than a firstpredetermined period and detects a second time period greater than asecond predetermined period, wherein the first time period is the timeduration for the input voltage to rise from a first voltage to a secondvoltage and the second time period is the time duration for the inputvoltage to drop from the second voltage to the first voltage.

In some examples, the dimmer detection unit determines that the LEDlighting system is connected to a TRIAC dimmer when the dimmer detectionunit detects a first time period greater than a first predeterminedperiod and detects a second time period smaller than a secondpredetermined period, wherein the first time period is the time durationfor the input voltage to rise from a first voltage to a second voltageand the second time period is the time duration for the input voltage todrop from the second voltage to the first voltage.

In certain examples, the LED lighting system includes a resistor-basedvoltage-divider network connected between the input voltage of the LEDlighting system and the ground. For example, the dimmer detection unitdetermines whether the LED lighting system is connected to a TRIACdimmer based on a change in a characteristic voltage of the inputvoltage. As an example, the characteristic voltage is obtained bydividing the input voltage using the resistor-based voltage-dividernetwork.

In some embodiments, a method for controlling an LED lighting systemincludes determining whether the LED lighting system is connected to aTRIAC dimmer using a dimmer detection unit based on a change in an inputvoltage of the LED lighting system, enabling a bleeder unit when the LEDlighting system is determined to be connected to a TRIAC dimmer, anddisabling the bleeder unit when the LED lighting system is determined tobe not connected to any TRIAC dimmer. As an example, the bleeder unitprovides a bleeder current sufficient for the TRIAC dimmer to worknormally when the LED lighting system is connected to the TRIAC dimmer.

In some examples, the method for controlling an LED lighting systemincludes determining that the LED lighting system is connected to aTRIAC dimmer when the dimmer detection unit detects a first time periodsmaller than a first predetermined period, wherein the first time periodis the time duration for the input voltage to rise from a first voltageto a second voltage.

In certain examples, the method for controlling an LED lighting systemincludes determining that the LED lighting system is not connected toany TRIAC dimmer when the dimmer detection unit detects a first timeperiod greater than a first predetermined period and detects a secondtime period greater than a second predetermined period, wherein thefirst time period is the time duration for the input voltage to risefrom a first voltage to a second voltage and the second time period isthe time duration for the input voltage to drop from the second voltageto the first voltage.

In some examples, the method for controlling an LED lighting systemincludes determining that the LED lighting system is connected to aTRIAC dimmer when the dimmer detection unit detects a first time periodgreater than a first predetermined period and detects a second timeperiod smaller than a second predetermined period, wherein the firsttime period is the time duration for the input voltage to rise from afirst voltage to a second voltage and the second time period is the timeduration for the input voltage to drop from the second voltage to thefirst voltage.

In certain examples, the method for controlling an LED lighting systemincludes determining whether the LED lighting system is connected to aTRIAC dimmer based on a change in a characteristic voltage of the inputvoltage, wherein the characteristic voltage is obtained by dividing theinput voltage using a resistor-based voltage-divider network of the LEDlighting system.

In some embodiments, an LED lighting system and a method for controllingthe LED lighting system determine whether the LED lighting system, whenpowered-on, is connected to a TRIAC dimmer based on a change in an inputvoltage of the LED lighting system. For example, by enabling anddisabling a bleeder unit based on the determination result, the LEDlighting system can adaptively eliminate the waste of system power thatis caused by the bleeder unit when the LED lighting system does notinclude any TRIAC dimmer, thereby improving the system efficiency.

In certain embodiments, an LED lighting system and a method forcontrolling the LED lighting system are provided. For example, the LEDlighting system includes a dimmer detection unit and a bleeder unit,wherein the dimmer detection unit determines whether the LED lightingsystem is connected to a TRIAC dimmer based on a change in an inputvoltage of the LED lighting system. In some examples, the dimmerdetection unit enables the bleeder unit when the determination result ispositive and disables the bleeder control unit when the determinationresult is negative. As an example, when the LED lighting system isdetermined to be connected to a TRIAC dimmer, the bleeder unit providesa bleeder current sufficient for the TRIAC dimmer to work normally. Insome examples, the LED lighting system can adaptively eliminate thewaste of system power that is caused by the bleeder unit when the LEDlighting system does not include any TRIAC dimmer, thereby improving thesystem efficiency.

According to certain embodiments, the present invention can beimplemented in other examples without departing from one or moreessential characteristics. As an example, various embodiments are to beconsidered in all aspects as exemplary but not limiting.

For example, some or all components of various embodiments of thepresent invention each are, individually and/or in combination with atleast another component, implemented using one or more softwarecomponents, one or more hardware components, and/or one or morecombinations of software and hardware components. As an example, some orall components of various embodiments of the present invention each are,individually and/or in combination with at least another component,implemented in one or more circuits, such as one or more analog circuitsand/or one or more digital circuits. For example, various embodimentsand/or examples of the present invention can be combined.

Although specific embodiments of the present invention have beendescribed, it will be understood by those of skill in the art that thereare other embodiments that are equivalent to the described embodiments.Accordingly, it is to be understood that the invention is not to belimited by the specific illustrated embodiments, but only by the scopeof the appended claims.

1.-35. (canceled)
 36. A system for controlling one or more lightemitting diodes, the system comprising: a dimmer detector configured to:determine that a rectified voltage is associated with a TRIAC dimmer ifa first time duration for the rectified voltage to increase from a firstvoltage to a second voltage is smaller than a first predeterminedduration or a second time duration for the rectified voltage to decreasefrom the second voltage to the first voltage is smaller than a secondpredetermined duration; generate a control signal to turn on a bleederif the rectified voltage is determined to be associated with a TRIACdimmer so that the bleeder generates a current, the current being largerthan zero in magnitude; and generate the control signal to turn off thebleeder if the rectified voltage is determined not to be associated withany TRIAC dimmer so that the bleeder does not generate the current. 37.The system of claim 36 wherein: the dimmer detector is furtherconfigured to determine that the rectified voltage is associated with aTRIAC dimmer; the first time duration is larger than the firstpredetermined duration; and the second time duration is smaller than thesecond predetermined duration.
 38. The system of claim 36 wherein: thedimmer detector is further configured to determine that the rectifiedvoltage is associated with a TRIAC dimmer; the first time duration issmaller than the first predetermined duration; and the second timeduration is smaller than the second predetermined duration.
 39. Thesystem of claim 36 wherein the dimmer detector is further configured todetermine whether or not the first time duration for the rectifiedvoltage to increase from the first voltage to the second voltage issmaller than the first predetermined duration based at least in part ona change of an input voltage.
 40. A method for controlling one or morelight emitting diodes, the method comprising: determining that arectified voltage is associated with a TRIAC dimmer if a first timeduration for the rectified voltage to increase from a first voltage to asecond voltage is smaller than a first predetermined duration or asecond time duration for the rectified voltage to decrease from thesecond voltage to the first voltage is smaller than a secondpredetermined duration; generating a control signal to turn on a bleederif the rectified voltage is determined to be associated with a TRIACdimmer so that the bleeder generates a current, the current being largerthan zero in magnitude; and generating the control signal to turn offthe bleeder if the rectified voltage is determined not to be associatedwith any TRIAC dimmer so that the bleeder does not generate the current.41. The method of claim 40 further comprising: determining that therectified voltage is associated with a TRIAC dimmer; wherein: the firsttime duration is larger than the first predetermined duration; and thesecond time duration is smaller than the second predetermined duration.42. The method of claim 40 further comprising: determining that therectified voltage is associated with a TRIAC dimmer; wherein: the firsttime duration is smaller than the first predetermined duration; and thesecond time duration is smaller than the second predetermined duration.43. The method of claim 40 wherein determining that the first timeduration for the rectified voltage to increase from the first voltage tothe second voltage is smaller than the first predetermined duration isbased at least in part on a first change of an input voltage.
 44. Themethod of claim 43 wherein determining that the second time duration forthe rectified voltage to decrease from the second voltage to the firstvoltage is smaller than the second predetermined duration is based atleast in part on a second change of the input voltage.
 45. A system forcontrolling one or more light emitting diodes, the system comprising: adimmer detector configured to: determine that a rectified voltage isassociated with a TRIAC dimmer if a first time duration for an absolutevalue of a voltage to increase from a first voltage to a second voltageis smaller than a first predetermined duration or a second time durationfor the absolute value of the voltage to decrease from the secondvoltage to the first voltage is smaller than a second predeterminedduration; generate a control signal to turn on a bleeder if therectified voltage is determined to be associated with a TRIAC dimmer sothat the bleeder generates a current, the current being larger than zeroin magnitude; and generate the control signal to turn off the bleeder ifthe rectified voltage is determined not to be associated with any TRIACdimmer so that the bleeder does not generate the current.
 46. The systemof claim 45 wherein: the dimmer detector is further configured todetermine that the rectified voltage is associated with a TRIAC dimmer;the first time duration is larger than the first predetermined duration;and the second time duration is smaller than the second predeterminedduration.
 47. The system of claim 45 wherein: the dimmer detector isfurther configured to determine that the rectified voltage is associatedwith a TRIAC dimmer; the first time duration is smaller than the firstpredetermined duration; and the second time duration is smaller than thesecond predetermined duration.
 48. The system of claim 45 wherein thedimmer detector is further configured to determine whether or not thefirst time duration for the absolute value of the voltage to increasefrom the first voltage to the second voltage is smaller than the firstpredetermined duration based at least in part on a change of an inputvoltage.
 49. A method for controlling one or more light emitting diodes,the method comprising: determining that a rectified voltage isassociated with a TRIAC dimmer if a first time duration for an absolutevalue of a voltage to increase from a first voltage to a second voltageis smaller than a first predetermined duration or a second time durationfor the absolute value of the voltage to decrease from the secondvoltage to the first voltage is smaller than a second predeterminedduration; generating a control signal to turn on a bleeder if therectified voltage is determined to be associated with a TRIAC dimmer sothat the bleeder generates a current, the current being larger than zeroin magnitude; and generating the control signal to turn off the bleederif the rectified voltage is determined not to be associated with anyTRIAC dimmer so that the bleeder does not generate the current.
 50. Themethod of claim 49 further comprising: determining that the rectifiedvoltage is associated with a TRIAC dimmer; wherein: the first timeduration is larger than the first predetermined duration; and the secondtime duration is smaller than the second predetermined duration.
 51. Themethod of claim 49 further comprising: determining that the rectifiedvoltage is associated with a TRIAC dimmer; wherein: the first timeduration is smaller than the first predetermined duration; and thesecond time duration is smaller than the second predetermined duration.52. The method of claim 49 wherein determining that the first timeduration for the absolute value of the voltage to increase from thefirst voltage to the second voltage is smaller than the firstpredetermined duration is based at least in part on a first change of aninput voltage.
 53. The method of claim 52 wherein determining that thesecond time duration for the absolute value of the voltage to decreasefrom the second voltage to the first voltage is smaller than the secondpredetermined duration is based at least in part on a second change ofthe input voltage.